Description and use of municipal solid waste composts in New Mexico

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The average American generates approximately 4.5
pounds of garbage per day, for a total of 196 million tons
of trash per year, most of which ends up in landfills
(Shortridge, 1993). Various government and private
programs have been organized to divert part of this
garbage (metals, plastics, paper and cardboard, and
yard and food wastes) from landfills by recycling. Yard
and food wastes often are recycled as compost.
A 1991-1992 landfill survey showed that yard waste
made up 33.8 percent of the City of Albuquerque’s
residential solid waste stream (Romo, Cave, and Watkins,
1992). During the same period, the city’s wastewater
treatment facility was treating more than 50 million
gallons of mixed residential and industrial wastewater
daily, producing about 22 dry tons of stabilized biosolids
(sludge) per day.
To address these solid waste problems, the City of
Albuquerque dedicated a state-of-the-art municipal com-post
facility in early 1992. Since then, portions of the
source-separated landscape wastes (2,500 ton/year of
yard trimmings) have been combined with biosolids
(9,700 ton/year) and horse track manure (3,600 ton/
year) at the facility to create an EPA-certified (Class A)
biosolid compost (Glass, 1997). In 1996, the same
facility began making a green waste compost using urea
(fertilizer) instead of biosolids as a nitrogen source.
Other municipal composting operations in New Mexico
are located at Artesia, Los Alamos, Alamogordo,
Carlsbad, and Tucumcari (Baker, 1998). A number of
private companies compost yard wastes, and permits
are pending for other municipal composting programs.
COMPOSTING VERSUS LANDFILLING
Yard wastes and biosolids not only occupy valuable
space in landfills, but they also decompose, which can
result in the production of methane gas and leachates
that pollute the environment. Also, collection of yard
waste is expensive. Recycling these organic wastes as
composts benefits the environment, and financial re-turns
from the sale of municipal composts can help
offset the costs of collection and processing. Recycling
the composts back on city parks, in local gardens, on
farms, or for revegetation of disturbed lands, also can
make such entities more sustainable.
THE COMPOSTING PROCESS
Composting is the aerobic, biological degradation
and oxidation of organic wastes such as manures,
biosolids, food scraps, and yard trimmings by various
naturally occurring microorganisms under controlled
conditions which results in a stabilized, humus-like
material.1
Municipal solid waste composting is composting on
a community-wide scale. Most municipal solid waste
composting facilities in New Mexico are source-sepa-rated
operations where yard wastes are separated from
other wastes such as cans and plastic. Biosolid composts
are co-composted products where biosolids are com-bined
with yard wastes. Green waste composts gener-ally
only involve yard wastes and the possible addition
of a nitrogen fertilizer.
Optimum composting conditions involve a balance
of six factors: (1) the carbon:nitrogen ratios of feed-stocks,
(2) particle size, (3) oxygen, (4) moisture, (5)
temperature, and (6) time. The composting process
involves the generation of heat, production of carbon
dioxide, loss of water vapor, loss of mass (waste), and
production of a relatively stable humus that is free of
offensive odors.
Description and Use
of Municipal Solid Waste Composts
in New Mexico
George W. Dickerson, Extension Horticulture Specialist
1 The criteria for “stabilized” compost vary somewhat, but in general, a
compost is considered stable when the temperature in a static pile remains
at or near ambient air temperatures for several days; moisture content is
about 50 percent; and oxygen content is more than 5 percent.